When teaching competitive swimming, it is important that each hand and arm movement be mastered for each stroke (freestyle, breast stroke, butterfly, etc.). One of the more difficult parts of teaching a swimming stroke is movement of the arms during the pushing or power phase of each stroke. Young swimmers arc shown stroke movements while standing vertically on dry land. This is very unlike moving forward horizontally through the water. Coaches can observe and critique swimming students while in action, but it is very difficult to provide real-time feedback as to whether each hand movement was executed correctly.